Lead is a well recognized environmental and occupational toxicant that is widely distributed throughout the United States. Current research has suggested a variety of biological effects,especially at high doses. These studies were an effort to find a more sensitive model for long-term low level lead exposure with analysis of serum gonadotropins and testosterone as well as sequential sperm analysis in rabbits as the end points for effect. The first year's study suggested that the low doses selected were effective in altering reproductive function and that this model will provide data for extrapolation of low dose effects of lead in men. Additional dose groups are being studied in the second of this series of investigations with greater focus on correlating blood levels with physiologically significant effects.